In the molding art, including injection molding, die cast molding, rubber molding, or the like, typically a pair of relatively movable first and second dies are employed to mold a desired object. However, before the die assembly may be operated, there must be assurance that the dies are properly aligned relative to each other. In order to accomplish this, guide pins have been typically employed in the past. Usually, the guide pins are mounted within one of the dies, and each includes a portion extending above the surface of the die for entering one of a plurality of aligning passageways formed in the other die for receiving the respective guide pins to align the dies.
However, the problem with such an arrangement is that when the die assembly is operated to mold a desired object, typically the two die sections of the die assembly are heated to different temperatures so that there is a differential expansion problem. This causes one of the die sections of the die assembly to expand to a greater extent than the other die section, so that the aligning passageways on one die are moved out of alignment with the guide pins of the other die. As a result, during subsequent molding operations of the die assembly, because the guide pins are no longer properly aligned with the aligning passageways, the guide pins and/or passageways are damaged or scored. Accordingly, it would be desirable to provide an arrangement which overcomes these problems.
Broadly, it is an object of the present invention to provide an improved guide pin assembly for dies which overcomes the aforesaid problems. Specifically, it is within the contemplation of the present invention to provide guide pin assemblies which include detachable aligning pins which may be detached from the guide pin assembly after the dies have been aligned and are ready to be used in order to avoid any problems of scoring and/or damaging the guide pins and/or aligning passageways of the die assembly.
It is a further object of the present invention to provide an arrangement wherein the guide pin assembly is formed in sections so that the section extending above the surface of the first die for entering one of a plurality of aligning passageways of a second die for aligning the first and second dies in detached after the first and second dies have been aligned, so that damage to the guide pins caused by differential heating of the first and second dies is avoided.
It is a still further object of the present invention to provide in an alternative embodiment an arrangement wherein each of the guide pin assemblies includes a detachable aligning pin section which may be replaced with a replacement aligning pin section which includes unsymmetrical wall sections to compensate for uneven expansion of the first and second dies.